• 산업식품공학
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• 제23권1호
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• pp.55-61
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• 2019

딸기에 대해 pallet 상부와 하부는 PA 필름으로, 측면은 LLDPE 필름으로 MAP 처리를 할 경우 포장 내부의 온습도 편차를 줄이며, 산소 농도 3-6%, 이산화탄소 농도 15-25%로 안정화하여 감모율이 향상되고, 곰팡이 발생률이 억제되는 것을 확인하였다. 경도향상과 이취를 고려하였을 때 적정 이산화탄소 농도는 15-20%이며, 이러한 높은 이산화탄소 농도는 경도를 21-40% 수준으로 높이는데 영향을 준것으로 판단된다. 대조구의 경우 60% 숙도 딸기의 경도가 80% 숙도에 비해 높았으나, MAP 처리구의 경우 12일차를 제외하고 60%와 80% 숙도의 경도는 통계적인 차이 없이 높은 수준으로 유지되었다. MAP 처리 시 80% 숙도는 60% 숙도에 비해 감모율, 곰팡이 및 경도 차이 없이 0.7-2.4 °Brix 높은 당도가 유지되었다. 따라서, pallet MAP를 사용할 경우 동남아시아 국가로 선박 수출하기 위한 14일 동안의 선도유지가 가능하고, 80% 이상의 높은 숙도로 딸기를 수출하여 품질 경쟁력도 향상시킬 수 있을 것으로 판단된다.

• 한국식품영양과학회지
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• 제23권5호
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• pp.792-798
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• 1994

In order to investigate the antioxidant activity of phenolic compounds contained in domestic Meju and Doenjang , the methanolic extract from defatted Meju and Doenjang was fractionated into the phenolic acid and the isoflavone fractions by alumina column and polyamide-6 column chromatography, respectively. Both phenolic acid and isoflavone fractions exhibited an identical antioxidative effect against the oxidation of linoleic acid. GC analysis revealed that the phenolic acid fractio contained vanillic , chlorogenic ,p-coumalic , ferulic, and caffeine acid. The content of caffic acid was greater than 70% in the phenolic acid fraction and the content of vanillic and chlorogenic acids were disappeared during fermentation, and thus, the facts are thought to be reasons for the low antioxidant activity of the phenolic aicd fraction from Doenjang. Similarly, the isoflavone fraction cotained daidzin, glycitin-65-0 glucosider and genistin and their aglycons such as daidzein, glyciten and genistein. The content of daidzin and genistin in Meju dramatically decreased at the early stage of fermentation ,whereas the content of daidzein an dgenistein rather increased ; however, these change in isoflavone contents did not affect the antioxidant activity of isoflavone fractions.

• Membrane and Water Treatment
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• 제10권2호
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• pp.113-120
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• 2019

To investigate surface properties and interception performances of the new modified PVDF membrane coated with Graphene Oxide (GO) and nano-$TiO_2$ (for short the modified membrane) via the interface polymerization method combined with the pumping suction filtration way, filtration experiments of the modified membrane on Humic Acid (HA) were conducted. Results showed that the contact angle (characterizing the hydrophilicity) of the modified membrane decreased from $80.6{\pm}1.8^{\circ}$ to $38.6{\pm}1.2^{\circ}$. The F element of PVDF membrane surface decreased from 60.91% to 17.79% after covered with GO and $TiO_2$. O/C element mass ratio has a fivefold increase, the percentage of O element on the modified membrane surface increased from 3.83 wt% to 20.87%. The modified membrane surface was packed with hydrophilic polar groups (like -COOH, -OH, C-O, C=O, N-H) and a functional hydrophilic GO-polyamide-$TiO_2$ composite configuration. This configuration provided a rigid network structure for the firm attachment of GO and $TiO_2$ on the surface of the membrane and for a higher flux as well. The total flux attenuation rate of the modified membrane decreased to 35.6% while 51.2% for the original one. The irreversible attenuation rate has dropped 71%. The static interception amount of HA on the modified membrane was $158.6mg/m^2$, a half of that of the original one ($295.0mg/m^2$). The flux recovery rate was increased by 50%. The interception rate of the modified membrane on HA increased by 12% approximately and its filtration cycle was 2-3 times of that of the original membrane.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.453-462
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• 2017

PURPOSE. The purpose of this study was to investigate the in vitro cytotoxicity of thermoplastic denture base resins and to identify the possible adverse effects of these resins on oral keratinocytes in response to hot water/ food intake. MATERIALS AND METHODS. Six dental thermoplastic resin materials were evaluated: three polyamide materials (Smile tone, ST; Valplast, VP; and Luciton FRS, LF), two acrylic materials (Acrytone, AT; and Acryshot, AS), and one polypropylene resin material (Unigum, UG). One heat-polymerized acrylic resin (Vertex RS, RS) was chosen for comparison. After obtaining extracts from specimens of the denture resin materials (${\phi}=10$ mm and d=2 mm) under different extraction conditions ($37^{\circ}C$ for 24 hours, $70^{\circ}C$ for 24 hours, and $121^{\circ}C$ for 1 hour), the extracts (50%) or serial dilutions (25%, 12.5%, and 6.25%) in distilled water were co-cultured for 24 hours with immortalized human oral keratinocytes (IHOKs) or mouse fibroblasts (L929s) for the cytotoxicity assay described in ISO 10993. RESULTS. Greater than 70% viability was detected under all test conditions. Significantly lower IHOK and L929 viability was detected in the 50% extract from the VP ($70^{\circ}C$) and AT ($121^{\circ}C$) samples (P<.05), but only L929 showed reduced viability in the 50% and 25% extract from LF ($37^{\circ}C$) (P<.05). CONCLUSION. Extracts obtained from six materials under different extraction conditions ($37^{\circ}C$, $70^{\circ}C$, and $121^{\circ}C$) did not exhibit severe cytotoxicity (less than 70% viability), although their potential risk to oral mucosa at high temperatures should not be ignored.

• 공업화학
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• 제10권5호
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• pp.682-689
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• 1999

본 연구는 용융법에 의한 폴리아미드 6,6과 EPM 및 EPM-g-MA와 블렌딩시 탄성 중합체 함유량, 조성비(wt %), 혼합온도, 혼합속도 등의 변화에 따른 이성분 PA 6,6/EPM(or EPM-g-MA) 블렌드물과 삼성분 PA 6,6/EPM/EPM-g-MA 블렌드물을 제조하여 블렌드물 내 탄성 중합체 평균 입자 크기, 입자 형상 및 분포 등의 변화를 분석하고, 이에 따른 블렌드물의 기계적, 열적 특성에 미치는 영향을 고찰하였다. 본 연구결과, 혼합속도 250 rpm하에서 압출기 내 다섯 영역의 온도를 270, 265, 265, 255 및 $255^{\circ}C$로 변화시켜 탄성 중합체의 함유량 변화에 의하여 제조된 이성분 블렌드물중 높은 충격강도는 PA 6,6/EPM-g-MA(70/30) 블렌드물에서 확인되었으며 폴리아미드 6,6의 충격강도에 비하여 25배 증가하였다. 동일한 압출기 내 조건하에서 제조된 삼성분 블렌드물 중 PA 6,6/EPM/EPM-g-MA(70/15/15) 블렌드물 내 탄성 중합체 평균 입자크기는 $0.56{\mu}m$이면서 고른 입자분포를 나타내었으며 충격강도는 제조된 모든 블렌드물 중 가장 높았다. 이러한 블렌드물의 조성비하에서 혼합온도와 혼합속도 변화에 의하여 제조된 블렌드물의 기계적 특성과 블렌드물 내 탄성 중합체 분산정도는 감소하였다.

• 공업화학
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• 제10권4호
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• pp.563-567
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• 1999

용질배제율이 우수한 나권형 FT-30 폴리아미드 복합막을 상용하여 cephalosporin C를 농축하기 역삼투 농축실험을 하였다. $4{\sim}20kg/cm^2$의 압력과 100~1000 mg/L의 농도, 그리고 2.8과 5.6 L/min의 유속을 갖는 실험 조건하에서 cephalosporin C 수용액의 수투과율과 용질의 배제율 및 물질전달 계수를 구하였다. Cephalosporin C를 분리하는데 있어서 압력이 증가함에 따라 투과 플럭스가 증가하는 것으로 나타났다. 이 결과는 Kedem-Katchalsky 모델에서 예측한 것과 일치하였다. 그리고 배제율은 1에 가까웠다. 또한 공급액의 농도가 증가할수록 cephalosporin C의 배제율은 낮아지는 것으로 나타났다. 배제율은 고농도보다는 저온도에서 높게 나타났으나 그 감소 정도는 작았다.

• Elastomers and Composites
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• 제44권3호
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• pp.274-281
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• 2009

음이온중합기구으로 나이론 6와 나이론공중합체를 합성하였다. 나이론탄성체는 카프록락탐과 이소시아네이트로 활성화된 폴리올을 음이온중합기구을 통해서 공중합을 하였다. 전기방사공정으로 제조된 나이론과 나이론공중합체는, FE-SEM으로 구조를 분석한 결과, 100$\sim$180 nm의 직경을 갖는 나노섬유들로 이루어진 다공성 부직포였다. DSC와 ATR FT-IR을 이용하여 결정화거동 및 구조를 분석하였다. 인장실험을 한 결과 나이론은 나이론탄성체에 비해서 인장강도는 크고, 신율은 감소된다. 결정영역인 PA블록과 무정형인 PE블록으로 된 나이론공중합체인 나이론 탄성체는 PE블록 비율이 클수록 인장강도는 낮아지고 신율은 증가된다. $O_2$와 $N_2$를 반응기체로 한 상압플라즈마로 전기방사된 나이론과 나이론탄성체의 부직포표면을 개질한 결과, 개질된 부직포표면은 표면개질 전보다 더 친수성을 보였으며 반면에 $CH_4$를 반응기체로 사용한 상압플라즈마로는 부직포표면을 개질하면 부직표면은 소수성을 나타내었다.

• Design & Manufacturing
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• 제17권2호
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• pp.9-14
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• 2023

In this study, an experiment was conducted to confirm the applicability of the external shape control of the ultrasonic knife to the CFRTP material, which is the base material of thermoplastic. TC910 based on polyamide6 (PA6) was used as the material. The slope 와 and tool transfer speed of the material and tool were selected as process factors for processing, and the following results were obtained. Under all cutting conditions using an ultrasonic knife, friction heat caused by high-frequency vibration was issued at 150℃ at the contact part between the material and the knife during cutting. As a result of the cutting force analysis, the faster the transfer speed, the higher the cutting force as the angle of entry of the blade increased, and the size of the cutting force changed during cutting. As for the size of the burr in accordance with the transfer speed condition, the smallest burr occurred at 150mm/min in the side part, and the smallest burr occurred at 150mm/min and 200mm/min in the case of the outlet burr. The size of the burr according to the entry angle tended to decrease as the tool entry angle increased, and the side part tended to increase as the tool entry angle increased. As a result of the cutting surface analysis, it was confirmed that the base material was eluted under all conditions, and the faster the transfer speed, the lower the elution phenomenon of the base material. Based on the above results, cutting the CFRTP material with an ultrasonic knife is possible, but the effect on heat generation caused by friction needs to be minimized, and further research needs to be conducted on this.

• Composites Research
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• 제30권6호
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• pp.365-370
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• 2017

탄소섬유 강화 열가소성 수지 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 물성은 다양한 요인들에 영향을 받는다. 그 중에서도 탄소섬유 표면에 Sizing되어 있는 에폭시(Epoxy) 층은 열가소성 수지와 상호 작용(Interaction)이 없어 매우 취약한 계면을 형성하며, 열가소성 수지의 높은 용융 점도(Melting viscosity)는 탄소섬유 다발(Bundle) 사이로 함침(Impregnation)이 어려워 탄소섬유 강화 복합재료 내부에 기공(Void)를 형성한다. 이와 같이 탄소섬유와 열가소성 수지 간의 낮은 계면전단강도(Interfacial shear strength)은 탄소섬유강화 열가소성 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 기계적 물성을 저하시키는 가장 중요한 요인 중 하나이다. 따라서, 본 연구에서는 열가소성 수지와의 상호작용이 없는 탄소섬유 표면의 에폭시 층을 열풍을 통해 제거하고, 열가소성 수지의 점도를 낮춰 함침도를 향상시키기 위해서 용액형 열가소성 수지를 제조하여 탄소섬유 표면에 Sizing 처리 함으로써 CFRTPs의 물성을 향상시켰다. CFRTPs의 층간전단강도(Interlaminar shear strength; ILSS) 및 굽힘 강도(Flexural strength)를 통해 이를 검증하였으며, 수지의 함침도는 기공률(Void content)의 계산을 통해 분석하였다.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3348-3354
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• 2011

Oleanolic acid (OA) as template molecule, polyamide-6 (PA6) as basement membrane and poly(styrene-comaleic acid) (PSMA) were used to prepare PA6/PSMA-OA molecularly imprinted composite membranes by phase inversion method in supercritical $CO_2$ ($ScCO_2$). The template molecule (OA), [poly(styrene-co-maleic anhydride) (PSMAH), PSMA, molecularly imprinted membranes (MIMs) imprinting OA and MIMs after elution were all characterized by Fourier transform infrared spectroscopy (FTIR). The conditions that were the mass ratio between PSMA and OA from 3:1 to 8:1, temperature of $ScCO_2$ from $35^{\circ}C$ to $50^{\circ}C$ and pressure of $ScCO_2$ 12 MPa to 17 MPa were studied. It was obtained the largest adsorption rate and purity of OA after adsorption of the resultant MIMs, 50.41% and 96.15% respectively. After using PA6 film and non-woven fabrics as basement membrane respectively, it was found that smaller aperture of PA6 was used as basement membrane, a higher adsorption rate and a higher purity of OA after adsorption of the MIMs were obtained, and so were the stability and reproducibility of the resultant MIMs. After template molecules being removed, the MIMs had effective selectivity hydrogen bonding to separately bind in the binary components to the template molecules-oleanolic acid.